96 



BULLETIN OF THE 



On breaking 



two feet. The cliloritic bed is well developed on tbo soutli side of 

 tbe creek, while the north side is more greenstone, and all along the 

 whole length of the ravine np to the Mis, a distance of one and one- 

 half miles, the horizontal beds of sandstone arc readily traced, dipping 

 sjightly north near the falls, and being horizontal at the opening of tlie 

 ravine into Torch Eiver valley, plainly showing that they rest uncon- 

 formably upon the trap range. On examining this sandstone more 

 carefully, we find that the strata are made up of alternating layers of 

 sandstone of reddish or yellowish grain, and of beds of loose sandstone 

 containing boulders ; some of the beds of boulders resembling what is 

 common on sca-shorcs as a mixture of mud and shingle, 

 open several of the small boulders taken in situ from the beds we find 

 that they consist mostly of reddish trap, but frequently we come across 

 perfectly well water-worn boulders of grayish trap containing amygdales, 

 identical with the trap of the copper range a short distance west from 

 these beds of sandstone, plainly showing that the sandstone was depos- 

 ited upon the shores of the ridge of trap forming Keweenaw Point, and 

 has not been uplifted by it as is stated by Foster and Whitney. The 

 case is totally different with the sandstone north of the range that lies 

 conformably upon the trap, but the sandstone of the southern side of 

 the mineral range in the vicinity of Torch Lake is plainly of a different 

 age, lying, as it does, unconformably upon the former." 



In some respects it would seem that Mr. Agasslz, in common with 

 many geologists, had misunderstood the views of Messrs. Foster and 

 Whitney. Their idea was that the traps and sandstone comprised the 

 same formation. The present visible portion of the eastern sandstone 

 had, like the western one, been laid down since the trappean overflows. 



After the deposition of the entire series a fissure was formed running 

 along the Point from its head to the western limits of the district. 



I 



This 



was attended in the northeastern portion by the protrusion of trap 

 forming the Bohemian Mountains, but towards Portage Lake the fissnr- 

 ing was accompanied only by the elevation of the sandstone and trap 

 west of the line, while that cast of it remained nearly horizontal. As no 

 stratified rock can rest conformably on the intrusive mass which uplifts 

 it, so the sandstone was not supposed to rest conformably on the Bohe- 

 mian trap. They also did not in their final report regard the sandstone 

 along this fissure at the Douglass Houghton fall as dipping southerly, 

 although Mr. Foster had stated so in a previous report to Dr. Jackson.* 

 That Messrs. Foster and Whitney had this idea was probably inferred 



« Senate Doc, 1849-50, III. 783. 



